BaseTools: rename ReadMe.txt to ReadMe.rst

The ReadMe file is now RST, so update the filename extension to match.

Signed-off-by: Rebecca Cran <rebecca@bsdio.com>
Cc: Bob Feng <bob.c.feng@intel.com>
Cc: Liming Gao <liming.gao@intel.com>

Reviewed-by: Bob Feng <bob.c.feng@intel.com>

BaseTools/ReadMe.rst

@@ -0,0 +1,41 @@
+This directory contains the EDK II build tools and template files.
+Templates are located in the Conf directory, while the tools executables for
+Microsoft Windows Operating Systems are located in the Bin\\Win32 directory, other
+directory contains tools source.
+
+Build step to generate the binary tools
+---------------------------------------
+
+Windows/Visual Studio Notes
+===========================
+
+To build the BaseTools, you should run the standard vsvars32.bat script
+from your preferred Visual Studio installation or you can run get_vsvars.bat
+to use latest automatically detected version.
+
+In addition to this, you should set the following environment variables::
+
+ * EDK_TOOLS_PATH - Path to the BaseTools sub directory under the edk2 tree
+ * BASE_TOOLS_PATH - The directory where the BaseTools source is located.
+   (It is the same directory where this README.rst is located.)
+
+After this, you can run the toolsetup.bat file, which is in the same
+directory as this file.  It should setup the remainder of the environment,
+and build the tools if necessary.
+
+Please also refer to the ``BuildNotes.txt`` file for more information on
+building under Windows.
+
+Unix-like operating systems
+===========================
+
+To build on Unix-like operating systems, you only need to type ``make`` in
+the base directory of the project.
+
+Ubuntu Notes
+============
+
+On Ubuntu, the following command should install all the necessary build
+packages to build all the C BaseTools::
+
+ sudo apt install build-essential uuid-dev